Automatic telephone system



Jan. 5 1926.

i c. aLoMAx AUTOMATIC TELEPHONE SYSTEM 1923 2 Sheets-Sheet 1 led June 25 -Imfen :1r- Elarence E. Lnmax Ja'n. 5 1926.

C. E. I 'OMAX AUTOMATIC TELEPHONE SYSTEM Filed June 25, 192:5 2 sheets-sheet 2 40 di .M

LLI

- INT/W- 1 Elarence E Lmax Patented Jan. 5, 1926.

' UNITED STATES PATENT OFFICE.`

CLARENCE-*11. LOMAX, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY,l OF CHICAGO, ILLINOIS, [al CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Applicationled .Tune 25, 1923.

To all whom 'it may concern.'

Be it known that I, CLAenNcn E. LoMAx,

Y .a citizen of the United States of America,

and a residentof Chicago,rCook County, and State of Illinois, have invented certain. new and useful Improvements in Automatic Telephone Systems, ofv which the following is a specification.

This invention relates in general to automatic telephone syst-ems and its` object, broadly stated, is to provide a new and improved' arrangement of trunking by using plunger (Keith) type primary line switches, and secondary finder switches associated with :lirst selectors.

The above pointed out object, together with others not specifically mentioned at this time, will be pointed out and explained more fully hereinafter, reference being had to the accompanying drawings comprising Figs. 1 and 2, of which Fig. 1 is a schemat-ic diagram of the trunking arrangement, while Fig. 2 shows circuit diagrams of the equipment in use.

Referring now particularly to Fig. 1, the trunking arrangement will first be briefly explained, as this will render it` easier to understand the circuits. This diagrammatic layout shows in simple form the truuking between localsubscriber lines A and first selectors E in an automatic exchange. For example, 100 subscriber lines A, terminating in plunger type primary line` switches C, have access to ten outgoing trunks, the selection of an idle trunk being controlled by the master switch D. The ten outgoing trunks terminate in secondary finder switch banks, and when a trunk is Seriali No.` 647,425.

ter operating to stand opposite an idle finder and selector, and permitting said wire to start the finder hunting for the seized trunk asy already mentioned.

Having explained the trunking arrangement adopted, the apparatus shown in thek circuit diagrams may now be briefly described. The substation A, Fig. 2, is an ordinary. automatic telephone substation having the usual talkingA instrumentalities and a calling device for controlling the automatic.V switches. terminati-eat the exchange in the individual line switch C, which is of the well known plunger type, modified however, in circuit arrangement, to be hereinafter explained in detail in connection with its operation.

The master switch Dis of the type shown and described in the U. S. Patent to Newforth, No. 13,901, reissued April 13, 1915, modified however, to include supervisory re lays and associatedsignal and start wire circuits.

The distributor O is a non-numerical switch mechanically of the well known rotary` type in which the wipers have no normal position and move in a forward direction only. Itsfunction is to stand opposite an idle finder, such as F, and connect the start wire thereto. Its stepping magnet is operated by a seized selector, such as E,

and it must contain at least as many contact points as there are pairs of selectors and finders 1n the group.

The secondary finder switch F 1s also a non-numerical switch mechanically 0f they well known rotary type in which the wipers have no normal position and move in a forward direction only. Its function is to hunt for a trunk seized by a primary line switch and, when found, operate to connect saine through to the selector E, and disconnect the hunting mechanism.

The first selector E, `shown only in part, is mechanically of the usual and well known Strowger vertical and rotary type, modified however, in circuit arrangement to send back ground potential, separate from the release trunk groundpotential, from the release relay to the stepping magnet of the distributer O.

The line conductors Having brieliy explained the purpose of the invention and the apparatus involved in carrying it out, the operation of the equipment may now be explained more in detail. For this purpose it will be assumed that the subscriber at substation A desires to obtain connection with aA subscriber (not shown) accessible by way of the first selector E.

lVhen the calling subscriber at substation A removes his receiver to initiate the call, an energizingcircuit is completed over the line conductors 11 and 12 for the line relay 1a of the line switch C. Upon energizing, line relay 14 closes a locking circuit at armature 21 for itself in series with the pullin winding 18, by way of ground at relay 30 and said relay, armature 21 and its working contact, lower winding of relay tt, winding 1S, resting contact of armature 31 and said armature, and grounded battery; closes a circuit at armature 20 for the hold winding 17, which is in multiple with winding 18, and places ground potential, by way of conductor 13, on the multiple test contacts in the banks of connector switches hailing access to the line of substation A, whereby said line is made busy. Pull-in winding 18, upon energizing, operates both the plunger arm 15 and the cut-off armature 1G; the former, through the medium of its plunger (not shown) forces the bank springs lO-13, inclusive, into engagement, respectively, with the contacts tft-47, inclusive, and the latter disconnects the line conductors 11 and 12 from the line relay 14 and from ground, respectively. By the engage-- ment of bank springs 1043, inclusive, with contacts al1-7, inclusive, the line, test., and holding conductors are extended to bank contacts 50-53, inclusive, of the finder switch F.

By the extension of the test conductor at spring 12 and contact 4G, ground potential is placed on test contact 52 and its multiples in the banks of the finders. It may be pointed out in this connection that the lower winding of relay 14 and the winding of relay 30 are of very low resistance, preferably not over a couple of ohms each, so that test contact 52 is brought substantially to ground potential, as stated.

By the extension of the holding conductor, at bank spring L11 and Contact 45 a circuit is closed from ground, relay 30, armature 21 and its working contact, lower winding of relay 14, working contact of armature 2O and said armature to the master switch D, whereby said switch is operated in the well known manner to advance the plungers of all the remaining idle line switches into position before the terminals of the next idle trunk line. During the operation of the master switch the branch circuit including the pull-in winding 18, is

open at armature 31, but the other branch circuit including the holding winding 1T, is sufficient to hold relay 11 energized, and plunger arm 15 in operated position.

Relay 30, upon energizing, closes a circuit at armature 31 for slow acting relay Relay 32, upon energizing, connects ground to start wire 3G at armature 35; and closes a circuit at armature 33, whereby a lamp L is lighted, and an audible alarm (not shown) is operated whenever this relay is held up for more than a predetermined number of seconds.

1f finder switch l? wipers :3l-57, inclusive, happen to be standing on the trunk contacts 50-53, inclusive, when the line switch C plunges and seizes this trunk, as shown, a circuit may be traced as follows: Grounded test contact 52, wiper 5G, lo ver winding of relay 65, grounded battery. Relay U5, upon energizing, opens the circuit of the motor magnet 58 at armature (52, thus preventing rotation of the switch. It' finder switch l? wipers .Slt-5?, inclusive, are not standing on the trunk seized by the line switch C, a circuit may be traced as follows: Grounded start wire 3U, wiper 73, contact T5, resting contact of armature G2 and said armature, resting contact of armature 59 and said armature, motor magnet 58, and grounded battery. Magnet 58 energizes and deenergizes over this circuit, thus operating to rotate the wipers Fill-5'?, inclasiif'e, into engagement with the seized trunk contacts, which in this case are 50-58, inclusive. lVhen the wipers reach the contacts, a eircuit is closed for relay G5 by the engagenient of test wiper 5G with grounded test contact 52, which relay, upon energizing, opens the circuit of the motor magnet 58, and closes the circuits of the line, holding and guard wire conductors through to selector lil.

The line relay 8O of selector l now hecoines energized over the circuit from ground, working contact of armature 1) and said armature, spring 10, contact -t-l-v. contact 50, wiper 51, armature (30 and its working contact, armature Sel; and its resting contact, upper winding of relay 80, to grounded battery; whereupon the release relay 8l energizes to connect ground to the release trunk conductor and guard conductor at armatures 82 and 83, respectively. 'l`he ground placed on the negative conductor 1; at armature 1f) thus forms a holding circuit' for relay 8O and helps to prevent preliminary impulses caused by accidental or other operations of the subscribers switchhook preliminary to the dialling of the desired number. The following circuit may now be traced: Ground, armature 82 and its working contact, working contact of armature (31 and said armature, wiper 55, contact' 51. contact L15, spring 41, armature 2() and its working contact, winding 18, resting conloo tact of armature 3l and said armature, to grounded battery. Relay and winding 17 are held energized in multiple over this circuit and the make busy condition, previously described, is transferred to it. Re-

lays 14 and 30 are shunted out and the former relay, upon deenergizing, removes ground from negative line conductor 12 at armature 19; opens thecriginal holding circuit at arinature 20; and opens; the circuitto relay 30 at armature'Ql.` Relay 80, upon deenergizing, removes lground from start conductor `3G. Relay32, upon deenergizing, opens the alarm circuit, containing lamp L, atl armature 33.

At the same time that relays 14 and 30 are shunted, a circuit may be traced from ground, working contact of armature 83 and said armature, working contact of armature 68 and said armature, contact 7 4, wiper 72, resting contact of armature 71 and said armature, motor magnet 70,v to grounded battery. Magnet--` now energizes and de energizes to rotate the wipers 72 and 7 3 into engagement with contacts leading to the first idle finder andselector switch combination. The selected idle finder is not startedbe'cause ground has already been removed from the start wire 36 by the falling back of relay 30.

The calling subscriber may now operate his calling device in accordance with the first digit of theV called number, and the selector E will lraise its wipers to the correct level and rotate in to select an idle trunk leading to a succeeding switch, whereupon its switching relay will operate to extend the connection. Ground potential kis returnedy from the last seized switch, up to and including the connector, over the holding conductor to hold up the preceding switches; all of which is in the usual an well known manner.

The calling subscriber will inally terminate the conversation, and will replace his receiver, bringing about the disconnection of the apparatus in the usual manner. Briefly, upon the deenergization of the line relay of the connector (not shown), its release relay deenergizes and breaks the holding circuit of the preceding switches, whereby all the switches including the selector E, finder switch F and line switch C are restored to normal position.

This same arrangement can obviously be used for other combinations of subscribers `Strowger vertical and rotary type 'switches may be used as'secondary finder switches if so desired.

The advanta, e in the use of plunger type primary switches with rotary type finder secondary switches isthat it increases the size and etliciencyv of the selector groups over those that could be obtained by using the straight plunger type primary switches alone, and accomplishes this object' without using the relatively expensive rotary switches as individual switches, and without using secondary line switches, which require complicated multipling of the primary trunks in the secondary groups and complicated group busying arrangements, etc.

Having described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

What I claim is:

1. In a telephone trunking system, a plurality of groups of individual line switches,

groups of trunk lines accessible to said' groups of line switches, there being one group of trunk lines for each Vgroup of line switches, a group of iirst selecting switches comprising a greater number of switches than there are trunk lines inany of said groups, the number of switches being, however, less than the total number of such trunk lines, finder switches inserted in the system between the said trunk linesr and rst selectors, each finder being directly connected to a particular first selector and having access to all of said trunk lines, means for operating a line switch and a finder switchtoconnect a calling subscribers. line with an idle first selector, and means in such selector controlled over the calling line for maintaining the operated line and finder switches in operated position.

2. In a telephone trunking system, a plurality of preselecting individual line switches, a group of non-preselecting finder switches, trunk lines connecting the banks of said line switches with the banks of said finder switches, a iirst selector switch individual to and directly connected with each finder switch, subscribers lines terminating in said line switches, means responsive to a call for operating a line switch and a finder switch in quick succession toy connect the calling line with an idle first selector, and means for operating such selector responsive to impulses transmitted from the calling station.

3. In a telephone trunking system, a plurality of groups of preselecting individual line switches, a single group of non-preselecting finder switches, trunk lines connecting the banks of said line switches with theI banks of said iinder switches,-a iirst selector switch individual to and directly connected with each finder switch, and a distributer switch controlled by said selector switches for preselecting idle linder switches.

4. In a telephone trunking system, a plurality of groups ot preselecting individual line switches, a single group ot non-preselcctiiig iiiider switches, trunk lines connecting the banks ot said line switches with the banks of said finder switches, a first selector switch individual to and directly connected with cach iinder switch, means associated with each group ot line switches responsive to the operation of a line switch in the group for controlling the starting ot' a iinder switch, a distributer switch by means ot which the control is exercised, and circuitarrangements controlled by the selector switches for maintaining said distributer switch in readiness to start an idle finder.

In a telephone system, subscribers lines, line switches individual to said lines, trunk lines accessible to said switches, first selectors, finder switches individual to said first selectors, respectively'. for connecting the same with said trunk lines, means controlled over a subscribers line responsive to the initiation ot a call thereon for automatically operating the line switch individual to such line and the finder switch associated with an idle selector to extend such calling line over one ot said trunk lines to such idle first selector, and means it'or then operating said first selector under the directive control ot the calling subscriber to extend the calling line in the direction ot' the called line. i

6. ln a telephone system, a subseribers line. a selector switch, means responsive to the initiation of a call thereon for extending said line to said selector, said means including a line switch individual to said line, and a finder switch individual to said selector, a release trunk conductor extending through said finder switch trom the line switch to the selector, cut-ofi1 and switching relays in said line and inder switches, respectively, connected to said conductor, and means in said selector i'oi connecting` a source of cui'- reiit to said conductor to energize said relays.

7. ln a telephone system, means including a line switch and a finder switch in serial relation and operable successively lor extending a line to a trunk line, a line relay iii said line switch and means tor disconnecting the saine troni the line when the line ,switch is operated, and a locking circuit tor holding said liuc relay energized while said tinde' is operating.

H. in a telephone system` means including serially related line and iindei switches t'or extending a line to a. trunk line, means responsive to a call on said line tor initiating the operation ot' said switches, means tor locking said line switch in operated position independent ot' control over the calling line while the liiidei switch operating, and means automatically responsive to the completion oic the operation ot the finder Jfor again placing said line switch under control et the calling line.

i). In a telephone system, a line, a switch individual to said line, trunk lines accessible to said switch at one end, a finder switch having access to said trunk lines at the other end, means responsive to a call on said line for operating said line switch to connect with an idle trunk line and tor starting said iinder in search of such trunl; line. said means including a line relay in said line switch, means tor disconnecting said line relay when the line switch is operated, and a locking circuit tor holding said line relay energized until after the linder switch has found the trunk line.

10. In a telephone system, a line, a switch individual to said line, trunk lines accessible to said switch at one end, a iindcr switch having access to said trunk lines at the other end, means responsive to a call on said line for operating said line switch to connect with an idle trunk line and for starting said linder in seaicli ot such trunk line` .said means including a line relay in said line switch disconnected when the switch is operA ated, a holding circuit for said switches including a conductor of the connected trank line, a locking circuit for said line relay etlective to supply current to said holding conductor while the tinder is oliierating, and means eii'ective after the finder has i'ound the connected trunk line t'oi' supplying` current to said conductor troni another point, whereupon said line relay is deenergized.

ll. ln a line switch having movable contacts 'for connecting the conductors ot a calling line, with the conductors ot an idle trunk line, a controlling line relay, and contacts on said line relay .ior directly grounding one ot' said movable contacts.

12. ln a line switch having access to a group ot trunk lines, means including a line relay tor operating the switch to connect with an idle one ot said trunk lines, and contacts on said line relay i'or grounding a tallcing conductor ot the connected trunk line.

lil. ln a telephone system, trunk lilies, line switches having access to said trunk lines at one end, iindei' switches having access to said trank lines at the other end, each ol said finder switches having its wipers normally in engagement with some one otl said lrunlt lines, mains tor operating a line switch to seize an idle trunk line` means lor starting an idle finder, and means lor preventing movement ot the iinder in question in case the wipers tliereot' are in engagement with the seized trunk line.

l'Tv. In a telephone system` trani; lines. line switches having access to said trunk lines at one end, linder switches having aecess to said trunk lines at the other end, each ot' said finder switches having its wipers lUU normally in engagement with some one of said truuk lines, an automatic Switch individual to each nder switch, means foi' operating a line switch to seize an idle trunk line, means for Causing an idle finder switch to hunt for the Seized trunk line in order to extend the same to the associated automatic switch, and means in the finder in question for at once extending the Seized truuk to suoli automatic switch in oase the finder switch Wipers happen to be already in e11- gagemeut with the seized trunk line.

In Witness whereof, I hereunto subscribe my name this 21st day of June, A. D., 1923.

CLARENCE E. LOMAX. 

